1. Field of the Invention
This invention relates to a method of cooling an engine for an automobile.
2. Related Technology
In a typical motor vehicle cooling circuit, coolant passes through a jacket surrounding the vehicle engine and its temperature rises. It then passes through the radiator, entering the radiator through a manifold and then passing through cooling tubes where air flows over the tubes to remove heat from and to reduce the temperature of the coolant before the coolant is re-circulated via a second manifold to the vehicle engine.
Cooling systems generally have a coolant pump for pumping coolant through the engine coolant circuit. A valve is conventionally provided to prevent coolant circulating through the radiator while the engine is warming up. The cooling system usually includes a fan for blowing air over the radiator in the event that the coolant becomes too hot in situations where the speed of the automobile does not provide the necessary cooling air flow over the radiator.
Known methods of cooling engines usually include controls based on output of a thermostatic device for opening and closing the valve and for switching the fan on and off. The speed of the water pump is generally operated in dependence upon the engine speed.
Such known systems use feedback from sensors in order to control the valve, the fan and the water pump. The emission levels and fuel economy achieved by an engine is known to be directly related to the operating temperature of the engine. An optimum temperature can be identified for any given engine; running the engine at this temperature for prolonged periods of time will result in reduced emissions and improved fuel economy.
However, due to the interactive nature of the individual system components it is possible to reject a given quantity of heat in a number of different ways. Ideally the components would controlled to optimize power consumption as well as emissions and fuel consumption.
The problem with known systems is that it is difficult to operate the engine at an optimum temperature in order to optimize emissions, while also optimizing fuel consumption and power consumption. Furthermore, traditional controllers such as proportional-integral-derivative (PID) controllers are based on comparing a measured value with a desired value (an error based approach) and calculates proportion, integrals and/or derivatives of the error in order to provide an adjusted input value. This approach requires large amounts of processor power and memory. Furthermore it assumes that the system being modeled is linear, or behaves as a monotonic function.
A simpler controller is sought which uses less system resources.